Air-heating system for heat-sealing containers



1968 F. HOFF 0 57 AIR'HEATING SYSTEM FOR HEAT-SEALING CONTAINERS Filed Sept. 29, 1965 5 Sheets-Sheet 1 T'IE 1 BLOWER INVENTOR FRANGiS L. HOFF ArrRNsir Oct 1, 1968 F. L. HOFF 3,404,257

AIR-HEATING SYSTEM FOR HEAT-SEALING CONTAINERS Filed Sept. 29, 1965 5 Sheets-Sheet 2 8B i FIE EI :3 I mvsmon I I FRANCIS L. HOFF 2 I BY M /MJ ATTORNEY Oct. 1, was L, HOFF 3,404,257

AIR-HEATING SYSTEM FOR HEAT-SEALING CONTAINERS 5 Sheets-Sheet 5 Filed Sept. 29, 1965 158 I62 I32 F38 IE I G 7 INVENTOR FRANCIS L. HOFF BY M ATTORNEY United States Patent 3,404,257 AIR-HEATING SYSTEM FOR HEAT-SEALING CONTAINERS Francis L. Hoff, Santa Clara, Calif., assignor to FMC Corporation, San Jose, Calif., a corporation of Delaware Filed Sept. 29, 1965, Ser. No. 491,297 7 Claims. (Cl. 219374) ABSTRACT OF THE DISCLGSURE An air heating system for rendering the thermo-plastic coating of paper containers tacky prior to sealing such containers includes a turret having air directed through a tubular column into a closed rotatable housing which housing has a plurality of openings for slidably receiving heating assemblies. Each assembly has one end communicating with the housing and has a distribution nozzle on the other end. Means are provided within each assembly to define a series of elongated concentric tubular passageways which cause the air to flow progressively from the outer passageway to the innermost passageway, which innermost passageway has a heating element therein whereby the air is gradually raised to a desired temperature.

This invention relates to an air heating system and more particularly to improvements in heating air which serves to render the thermo-plastic coating of paper containers tacky prior to scaling such containers.

The present heating system is an improvement over the heating system disclosed in United States application of Vadas et al., Ser. No. 461,738, filed June 7, 1965 and assigned to the assignee of the present invention.

The present application is particularly concerned with improvements in the apparatus for heating those flaps of the carton which define the top closure whereas applicants copending application Ser. No. 491,275 filed Sept. 29, 1965, which application issued on Feb. 2, 1968 as Patent No. 3,367,642 and is assigned to the assignee of the present invention, is concerned with improvements in the apparatus for heating the flaps defining the carton bottom.

In the first above-referenced application a plurality of electrical resistance elements are located in stationary tubular housings having respective ends communicating with a manifold which supplies air to the resistance elements. As the air traverses the heating elements it is heated and passes through a rotary control valve, a rotary seal and through a rotary annular housing. Each of the top heaters is mounted on a hot air tube which receives heated air communicated to the annular housing. The air is then discharged against the flaps of the carton top by a nozzle structure.

Although the top heaters of the referenced application have fulfilled their intended function, various problems arose due to the location of the heaters with respect to the air distributing nozzles and the temperature at which it was required to operate the heaters in order to produce a desired air temperature at the discharge nozzles.

To illustrate by way of example, the electrical resistance heaters of the prior application were operated at a temperature of 1800 F. in order to maintain an air discharge temperature at the distributing nozzles of 600 R, which is the temperature required to render the plastic coating of the cartons tacky and thereby enabling the cartons to be sealed. In contrast the present invention will produce an air discharge temperature of 600 F. while operating the electrical resistance heaters at 900 F.

By operating the heating element at 1800 F., it was found that a rather rapid rate of corrosion occurred in the electrical heating element producing minute particles of scale which were induced in the air stream and eventually discharged into the carton rendering it useless for its intended purpose as a container for consumable liquids. When this condition was detected it was necessary to replace the electrical resistance elements.

Experience with the air heating system of the present invention has shown that its life is indefinitely long and that no problems of corrosion have arisen. Reduction in the temperature in which the electrical resistance element can be operated is mainly due to the fact that it is located immediately adjacent the air distributing nozzle and the fact that a novel system of air passages increases the amount of heat transferred to the air by the heating element.

Accordingly, it is an object of this invention to provide a new and improved apparatus for heating air, said apparatus being particularly useful for rendering the plastic coating of a carton tacky prior to sealing.

Another object of this invention is to reduce the path of travel of the air from the point at which it traverses the heating element to the discharge orifices of the distributing nozzle.

Another object of this invention is to locate the air heating elements closer to the points of discharge and thereby reduce the heat losses.

Another object is to reduce environmental temperature around a heating apparatus and to render certain surfaces of the apparatus cool enough for human contact.

Another object of this invention is to operate the heating element at a reduced temperature.

Another object of this invention is to operate the heating element at a temperature which prevents oxidation of the heating element.

Another object is to minimize the expense and increase the life of bearings used in a heating system.

Other objects will be evident and an understanding of the invention may be had by referring to the following description and claims taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a vertical central section of an apparatus which distributes hot air to the top flaps of a carton and which embodies the present invention.

FIGURE 2 is a transverse section taken substantially along the line 2--2 of FIGURE 1.

FIGURE 3 is a fragmentary side elevation of FIG- URE 2.

FIGURE 4 is an enlarged longitudinal section of an air heating and distributor head shown in FIGURE 1.

FIGURE 5 is a transverse section taken substantially along the line 55 of FIGURE 4.

FIGURE 6 is another transverse section taken substantially along the line 66 of FIGURE 4.

FIGURE 7 is yet another transverse section of FIG- URE 2 taken substantially along the line 7-7 of FIG- URE 2; and

FIGURE 8 is a fragmentary developed section taken substantially along the curved cutting plane 88 of FIGURE 6.

The major components of the air heating and distributing station shown in FIGURE 1 and generally designated by the numeral 10 include a central upwardly extending support structure 12 mounted on a base frame 14. A totally enclosed air plenum chamber 16 and a plurality of air heating assemblies 18 each having an air distributing nozzle 20 attached thereto, are arranged to be rotated about the support structure. A driving hub 22, driven by a chain 24 mounting carton carriers 26, causes rotation of the plenum chamber 16 and the air heating assemblies 18. The carton carriers 26 and the nozzles 20 are maintained in vertical alignment in order to provide registration of the nozzles with the upper flaps of the carton which is shown in phantom outlines and indicated by the letter C. A stationary hub 28, having a cam track 30, is provided for reciprocating each of the assemblies 18 as they rotate to locate the nozzles 20 in close adjacency with the carton flaps desired to be heated.

As shown in FIGURE 1 the support structure 12 comprises an upwardly extending elongate tubular column 32 having a bell-shaped lower end 34 rigidly secured to the frame 14 by bolts 36. The lower end of the column is provided with a closure plate 38 sealing the lower end of the column.

On the upper portion of the column 32 the hub 28 is rigidly connected thereto by a key 40 and is held against axial displacement relative to the column by lock nuts 42.

Rotatably mounted by means of bearings 44 and 46, and in concentric relation to the column 32, is a tubular shaft 48 to which is secured, in axially spaced relationship, a nozzle hub 50 and the driving hub 22. The driving hub is formed with an outwardly extending drive flange 52 to which is secured, by means of bolts 54, a sprocket 56. A splash pan 58 formed with an outwardly extending skirt 60 is also secured to the flange 52 by the bolts 54.

Although the driving hub 22 rotates with the tubular shaft 48 it is arranged so that it may be moved axially relative thereto. By virtue of this movement containers C of various lengths may be handled by the air heating and distributing station. The lower end of the driving hub 22 rests upon an annular transition support 62 through an annular thrust bearing 64. The support 62 is in turn mounted upon and rigidly secured to an adjustable frame 66 which is adapted to be raised and lowered, in the same manner as disclosed in said copending application, Ser. No. 461,738, so that the hub 22 may be accordingly raised and lowered.

The sprocket chain 24, on which are mounted carton carriers 26, is trained about the sprocket 56 and is operative to impart a suflicient amount of torque to cause rotation of the drive flange 52. Driving relationship between the drive flange and the nozzle hub 50 is established by a cylindrical pin 70 which is fastened to the flange 52 by bolt 71 and which passes through an aligned slider hearing 72 carried by the hub 50.

As shown in FIGURE 1 the air receiving plenum chamber 16 is formed by a lower wall 74 and a dome-like cover 76. The upper end of the tubular column 32 projects into the plenum chamber. The plenum chamber is supported in the illustrated position by a plurality of circumferentially spaced vertically extending rods 78 (FIG. 3). One end of each rod is rigidly connected to the nozzle hub 50 and the other end is rigidly connected to the plate 74. By this arrangement of parts it will be readily apparent that the plenum chamber 16 rotates with the hub 50.

The air heating assemblies 18, carrying the air distributing nozzles 20, are cylindrical in shape and have an upper reduced diameter tubular portion 80 slidably fitted through a seal 82 mounted on the lower wall 74 of the plenum chamber. The lower cylindrical portion 84 is fastened to a carrier 86 taking a form which is shown best in FIGURE 3. It will be seen that the carrier is formed with outwardly extending spaced leg portions 88 which are slidably mounted on one of the rods 78 and another oppositely directed leg portion 90 which is also slidably mounted on an adjacent one of the rods 78. The central portion of each carrier is formed with a bore 92 having one of the air heating assemblies 18 suitably detachably disposed in the bore. Each of the carriers 86 has an integral inwardly directed extension 94 rotatably mounting a cam follower roller 96 which rides on the cam track 30. Thus as the hub 22 is rotated by the chain 24, rotation of the nozzle hub 50, the plenum chamber 16, and the air heating assemblies 18 takes place through the agency of the drive pin 70. In addition, the air heating assemblies are caused to reciprocate during their rotation by the cam 30 which is rollingly engaged by the rollers 96 supported on each of the carriers 86.

As will be presently explained in detail, each air heating assembly 18 includes an electrical heating element 156. Electrical current is conducted to each heater while they are rotated and reciprocated. As shown in FIG- URE 1, an electrical conduit 98 extends through the bore of the tubular column 32 and through the closure plate 38. The lower end of the conduit is attached to the closure plate by lock nuts 100 and the upper end passes through a suitable bore formed in a cap 102 threaded to the upper end of the column 32. A plurality of slip rings 104 are mounted on the upper end of the conduit 98. Each of these slip rings is in frictional engagement with brushes 106 mounted on a bracket 108 which is secured to the lower plate 74 of the plenum chamber 16. Thus as the plenum chamber 16 rotates, the brushes 106 travel around the slip ring and thus maintain electrical contract.

A suitable number of conductors 110 are located within the conduit 98 and are attached to the slip rings 104 in a conventional manner enabling electrical current to be fed to the slip rings. Each of the brushes is provided with a suitable binding post 112 to which is attached a line 114. This line is also connected to an upwardly extending insulated bar 116 mounted on an annular ring 118 which is secured to the lower plate 74 of the plenum chamber 16. Each of the heating elements 156 located within the air heating assemblies 18 has a pair of upwardly extending insulated rods 120 (only one of which appears in FIG. 1) to which are attached suitable flexible conductors 122, preferably of the braided wire type, which are connected to the insulated bar 116 in contact with the line 114 so that current from the brushes is conducted to the heaters.

Referring now to FIGURE 4, there is shown a longitudinal section of one of the air heating assemblies 18. As will appear in the following description, each assembly receives air from the plenum chamber 16 and provides a flow path which gradually heats the air to the desired temperature while at the same time maintaining the outer surface or lower portion 84 cool enough so that it may be touched with the human hand without undue discomfort. This, of course, reduces heat losses due to conductance and radiation obviating the necessity of using high temperature-resistant materials for those parts, such as bearings and shafts, which are subject to such heat transfer.

As previously mentioned, the air heating assemblies 18 comprise cylindrical portions '80 and 84. As shown in FIGURE 4, both of these portions are tubular and are interconnected by an annular ring 124 preferably welded to such portions and define an annular passageway 126 which is closed at its lower end by another annular ring 128. An annular abutment 130 is secured within the bore of the member 80 and it has welded thereto a downwardly extending tube 132 which forms an annular passageway 134 radially inwardly of the annular passageway 126. Communication between these passageways is provided by a series of circumferentially spaced holes 136 extending through the cylindrical portion 80 and at the lower end thereof. Holes 138 are also provided through the tube 132 permitting the air supplied to each of the heating assemblies to be directed to the air distributing nozzles 20 as will be presently described.

The annular abutment ring 130 supports a round plate 140 to which is attached a tube 142 provided with an end plate 144 through which are threaded bolts 146. The tube 142 has welded at the outer surface thereof thin strips 148 which serve to hold an electrical resistance element 156 in a fixed position.

The air distributing nozzle 20 is in communication with the interior of the tube 132 by means of a short nipple 150 which is welded to a flange 152 secured to the annular ring 128 by a plurality of bolts 154.

Still referring to FIGURE 4, it will be seen that the heating element 156, in the form of a helix, is slidably fitted in surrounding relation to the tube 142 and it is held in spaced relation relative thereto by the strips 148. The heating element is releasably secured to the tube 142 by means of a small bar 158 extending through the holes formed in the tube 142 and a pair of U-shaped clips 160 which cradle the upper turns of the heating element and are provided with aligned holes in the leg portions through which the bar 158 extends. In assemblying the heating element 156 to the tube 142, the U-shaped clips are slipped on the upper turns of the heating element. Then the element is slipped over the tube .142 in alignment with the transverse hole in the tube. The bar 158 then is inserted through the holes in the U-shaped clips and the hole in the tube 142. Positive retention of the clips 160 on the bar 158 is insured by small retaining pins 162 extending through the bar 158.

The insulated rods 120 of the heating element 156 extend through holes (not shown) formed in the round plate 140 and are received within bores 166 formed in an upper stem 168. As shown in FIGURES 5 and 6 the stem includes, at its central portion, diametrically opposed lobe portions 170 having an integral narrow web 172 extending therebetween. The upper end of the stem is provided with diametrically opposed bores 174 formed in a radially extending flange 176 provided with a tapered surface portion 178 and a straight portion 180. The stem 168 is of sufiicient length so that the straight portion of the flange fits within the bore of the tube 80 while the insulated rods 120 of the heater element extend substantially beyond the upper surface of the stem. This is more clearly shown in FIGURE 4.

With the stem 168 resting on the circular Plate 140, it is held in this position by a retaining nut 182 threaded on the upper end of the member 80. The nut includes a tapered surface corresponding to the tapered surface 178 and it is effective to squeeze the flange 176 when it is tightened in order to hold the upwardly extending rods 120 against axial movement with respect to the stern 168. The flange 176 is slotted at 184 (FIG. 5) so that when the nut 182 is tightened, the effect of the tapered surfaces on the nut and the flange causes a clamping force to be imposed upon the rods 120.

The portion 'of the tubular member 80 located between the annular abutment 130 and the ring 124 is provided with a series of circumferentially spaced holes 186 which establish communication between the annular passageway 126 and the interior of the tubular portion. A short tubular sleeve 188 has its lower end seated against the annular abutment 130 and is provided with a series of circumferentially spaced holes 190 being preferably of the same diameter, the same number, and the same spacing as the holes 186. The short tube 188 is mounted in the tubular member 80 so that it may be easily rotated and in this manner it serves as a damper since, as shown in FIGURE 8, the holes 186 and 190 may be brought out of register and thereby reduce the total flow of air which is to be heated. In order to hold the short tube 188 in a desired angular relation with respect to the tubular member 80 a nut and bolt 192 extending through a slot 194 (FIG. 8) is provided. By merely loosening the bolt, the tube 188 may be rotated with respect to the tubular portion 80 in order to change the flow area.

Air from any suitable blower 195 is supplied to the plenum chamber 16 this air is permitted to flow to each of the air heating assemblies 18. -In accordance with an important features of this invention, the air is not heated until it passes through the various interconnected annular passageways shown in FIGURE 4. Referring now to FIG- URE 1, it will be seen that the lower bell-shaped end 34 of the tubular column 32 has a conduit 196 suitably attached thereto which conducts air from a conventional blower to the interior of the column 32. The cap 102 on the upper portion of the column has a plurality of large holes 197 (preferably four in number), allowing the air to be discharged into the plenum chamber 16. The air in this chamber is supplied to each of the air heating assemblies 18 by virtue of the holes 174. The air then passes downwardly through the upper portion of the tubular member through the holes 190* and 186 into the annular chamber 126.

While in the chamber 126, the air is slightly heated and it may assume a temperature of approximately be tween and degrees before it is communicated into the annular passageway 134 through the holes 136. While in this last mentioned passageway, the air increases in temperature since it is closer to the heating element 156. The air then flows through the holes 138 into the tube 132 downwardly and past the heating element 156. The air raises in temperature to an extent whereby the discharge temperature at the air distribution nozzle 20 is at approximately 600 degrees F. To achieve this air discharge temperature, experience has shown that it is merely necessary to operate the heating element 156 at approximately 900 degrees F.

It is a significant aspect of the above described structure that a system of gradually increasing the air temperature is provided which causes the air to flow through adjacent paths in opposite directions as it is heated. This principle is referred to as counterflow heat exchange and is a very efficient method of exchanging heat between fluids. In the present instance a single fluid is used to effect heat exchange of this type.

Thus, according to the above described invention, it should be readily apparent that it provides an arrangement of apparatus which heats air utilized for rendering the plastic coating of cartons tacky in a manner which does not require rotating seals to prevent the leakage of air. Furthermore the heat loss due to the various mechanisms of heat transfer is considerably reduced thereby lowering the environmental temperature since the air is heated to its desired temperature immediately before it issues from the air distributing nozzles. Not only does the above described construction reduce the complexity and number of parts required to perform this function, but it also renders unnecessary the utilization of very expensive and hard-to-work materials which were heretofore required due to the great amount of heat which was lost by conduction and radiation. Safety is enhanced because many exterior surfaces can now be normally touched without burning or undue discomfort. Furthermore, by operating the heating elements at approximately 900 degrees it has been found that they can perform their function for very long periods of time and that no problems of oxidation arise.

While a particular embodiment of the present invention has been shown and described, it will be understood that the apparatus is capable of variaton without departing from the principles of the invention, and that the scope of the invention should be limited only by the scope and proper interpretation of the claims appended thereto.

What is claimed is:

1. An air distribution system comprising a tubular stationary column, a support rotatably mounted on said column, a plenum chamber in communication with the bore of said column, said column having its bore in communication with a steam of moving air, said chamber being mounted on said support for rotation therewith, at least one air heating device communicating with said chamber, means in said air heating device defining a plurality of interconnected annular passageways which are in communication with said chamber and with the atmosphere, and a heating element in the innermost of said passageways for heating the air immediately before it is discharged to the atmosphere.

2. An air distribution system according to claim 1 when said air heating device comprises an air distributing head; said passageway defining means including an elongated hollow housing having said distributing head connected to one end thereof and having the remaining end in communication with said plenum chamber, said passageways being interconnected to direct the air flowing therethrough to reverse its direction of flow and progressively guide the air inwardly for movement past said heating element immediately before it is directed into said distributing head.

3. An air distribution system according to claim 2 wherein said heating device is operable to heat thermoplastic cartons, and wherein said elongated housing includes a cylindrical wall having a plurality of openings therein, a cylindrical tube movable relative to said cylindrical wall and having a plurality of openings therein, and means for locking said tube to said cylindrical wall with the opening therein selectively positioned in full or in partial registration with said openings in said cylindrical wall thereby adjusting the quantity of air flowing through said heating device.

4. An air distribution system according to claim 3 wherein a plurality of said air heating devices are disposed around the periphery of said plenum chamber, wherein a portion of each of said cylindrical walls remote from the associated heating element is movable relative to and pro jects into said plenum chamber, and additionally comprising means for sealing said cylindrical walls to said plenum chamber, and means for vertically reciprocating each of said air heating devices.

5. An apparatus for rendering the plastic coating of paper cartons tacky so that they may be sealed comprising a tubular support column having its bore in communication with a stream of flowing air, a frame rotatably mounted on said column and carrying an air plenum chamber and a plurality of air heating and distributing assemblies having outer walls, said plenum chamber and said heating and distributing assemblies being in communication with the stream of air supplied tothe bore of said column, a heating element in each of said heating assemblies near the center thereof, and means in each of said heating assemblies for causing the air supplied thereto to follow a sinuous path from adjacent the outer walls of each heating assembly inwardly adjacent the center thereof so that the air is gradually heated to a desired temperature.

6. An air heating apparatus according to claim 5 wherein each of said heating and distributing assemblies comprises a hollow elongate cylindrical housing, a transverse plate intermediate the ends of and mounted in the bore of said housing, a tubular member secured to said housing and defining a first outer annular passageway, another tubular member secured to said plate and located in the bore of said housing to define an inner annular passageway, a plurality of holes in the wall of said housing connecting that portion of its bore located above said plate with the outer passageway and additional holes in the wall of said housing connecting the outer annular passageway with the inner annular passageway, said heating element being an electrical heating element disposed in the bore of said another tubular member and being carried by said plate, and openings in the wall of said another tubular member establishing communication between the inner annular passageway and the bore containing said heating element, said passageways being interconnected to direct air admitted to the interior of said housing to flow successively in one direction for the entire length of the outer annular passageway, in a direction opposite to said one direction for the entire length of the inner annular passageway, and to traverse the length of said heating element to thereby effect a gradual heating of the air passing therethrough.

7. An apparatus for rendering the plastic coating of paper cartons tacky so that they may be sealed comprising a tubular support column having its bore in communication with a stream of flowing air, a frame rotatably mounted on said column and carrying an air plenum chamber and a plurality of air heating and distributing assemblies having outer walls, said plenum chamber and said heating and distributing assemblies being in communication with the stream of air supplied to the bore of said column, a heating element in each of said heating assemblies near the center thereof, and means in each of said heating assemblies for causing the air supplied thereto to follow a sinuous path progressively from a position adjacent the outer Walls of each heating assembly to a position near the center thereof so that the air is gradually heated to a desired temperature, said means comprising radially spaced longitudinally adjacent walls which define annular passageways, said passageways being in communication to define such a sinuous flow path which reverses the flow direction of the air in order to produce counter current flow and progressively guides the air inwardly toward said associated heating element thereby increasing the amount of heat conducted to the flowing References Cited UNITED STATES PATENTS 1,227,324 5/1917 Russell et a] 219-381 1,661,553 3/1928 Baar 219-364 2,819,378 1/1958 Noakes et al 219-381 X 3,094,606 6/1963 Ferris 219-370X 3,186,143 6/1965 Borkmann et al. 53-375 X 3,248,841 5/1966 Heffelfinger et al. 53-375 X 3,270,182 8/1966 Hynes 219-274 X FOREIGN PATENTS 90,337 12/ 1922 Austria. 936,648 9/ 1963 Great Britain.

ANTHONY BARTIS, Primary Examiner. 

